Testing instrument for machined parts



June 28, 1949. J., B. LovlcK 2,474,482

TESTING INSTRUMENT FR MACHINED PARTS Filed March 28, 1944 2 Sheets-Sheet 1 Arry.

June 28, 1949. J. B. LovlcK TESTING INSTRUMENT FOR MACHIN-ED PARTS 2 Sheets-Sheet 2 Filed March 28, 1944 INVENTOR. l f/H/vBLov/ck.

Patented June 28, 1949 UNITED STATES 'PATENT OFFICE TESTING INSTRUMENT FOR MACHINED PARTS John B. Lovick, Glendale, Calif., .assigner to Allied Appliance Go., Los Angeles, Calif., .a copartnership comprising William P. Todd and Milton C. Miller, Jr.

'Application March 28, 1944, Serial N0. '528,457

3 Claims.

tain machine tool .operations it is possible tol establish accurate dimensionsby the use of jigs .and fixtures. However, in "connection with the manufacture of certain parts this method is not infallible, particularly when parts are turned n a lathe or in an automatic screw machine. The

vpresent demand for high speed production of machinery .and equipment incident to war work has made it necessary to -provide'some means of rapidly and 'accurately measuring machined parts with relation to certain critical dimension-s. The usual method of .accomplishing this is by micrometer measurements. An experienced .and skilled inspector is required for this Work, and furthermore, it often occurs that critical measurements must be made Which'cann'ot be made quickly and with precision by the use of a micrometer or calipers. The demand for inspectors capable-of handling this type of testing is much ygreater than the supply, so that simple, accurate .and infallible means are necessary in order to use previously untrained inspectors who are not highly skilled. The principal object yof the present invention, therefore, is to .provide a testing instrument in which machined parts :may be placed quickly while being gripped at common points .as the part-s are successively placed in the instrument and removed,- .and :after which the part may be tested .for concentricity and for various lineal measurements within a predetermined set amount -of tolerance, lt'he instrument acting visually .to indicate Whether or not the machined part passes inspection oris rejected either .as `scrap or for y.remaclfiinhig operations.

The present invention `contemplates the provision of a bed plate carrying :a head and .tail .stock provided with :interchangeable chucks to receive a piece of work, and by which the work piece may `be rotatedloy. a driving unit, the structure carrying gauge elements associated with visual indicators to :apprise the operatoras to whether or not critical dimensions of the work 'piece are within Ia .predetermined limit `of tolerance.

'The .invention is illustrated by way of example .in the accompanyingnrawingsiin iwlrich.:

'head '.23 occurs.

Figure 1 is a view in plan showing the testing device with parts of the tail stock being indicated in longitudinal section.

Fig.f2 .is va viewin front elevation showing the testing instrument with parts of the head stock indicated in vertical section.

Fig. 3 is a view in vertical section through the testing instrument, as seen on the line 3-3.of Fig. 2, and shows the relative position of the driving `motor to the bed plate, as well vas the micrometer for testing concentricity and a gauge .finger for testing linear dimensions.

Fig` 4 is an enlarged'fragmentary view in verticalsection as seen on theline 4 4 oi Fig. 1, and shows the electric-switch gauge associated with the' tailstock. y

Fig. 5 is a view in diagram showing the indicating lamps and the wiring arrangement of the switchy gauges.

Fig. 6 is an enlarged viewin diagram indicating the critical dimensions of the work part and ,showing the manner in which the driving and "driven chucks engage the Work.

.Referring .more particularly to the drawing, t0 indicates abed plate `of the testing instrument, which is here shown as mounted upon supporting .legs VI I of'suitable length. Mounted upon the bed plate yis a X-ed head stock l2 and a longitudinal adjustable tail stock I3. The head stock is formed by a pair of parallel uprights I4 and I5, which are disposed 4at one end of the bed plate I0 andare suitably secured in horizontallyspaced relation to each other. Formed through the ilprights I4 and I5 and in horizontal longitudinal lalignment are bores I6 and I'I. These receive a driving spindle I8 which passes through the two uprights -and spans the intervening space. The opposite outer ends of the bores It and I-'I Iare counterbored, as shown at I9 and 2l!7 and receive .anti-friction bearings 2| and 22, respectively.

vouter Vend ofthe spindle I3 is formed with va.

threaded portion 24 receiving a thrust collar `25 whichbears against the inner race ofthe bearing 22 and is held in place by a nut 26. A central bore 21 is form-ed longitudinally in the end of the portion of the spindle I8 upon which the enlarged This bore receives a shank 28, upon the outer fend of which a driving chuck 129 is mounted. By reference to Fig. 6 of the drawing 'it will'zbe .seen that the driving chuck 29 is formed Withza shell-like outer Wall 30, the marginal lip s of which is formed with a bevel face 3l for a purpose to be hereinafter described.

Mounted upon the driving spindle i8 in the space between the uprights i4 and l5 is a worm gear 32. This gear is in mesh with a worin 33. The worm 33 is mounted upon a shaft 39 which extends horizontally beneath the gear 32 and with its axis at right angles to the axis of the spindle I8. Mounted upon the bed plate i9 in the rear of the uprights i4 and l5 is a bearing 35 through which the shaft 34 extends. The rear end of the shaft 34 carries a pulley 36 which is in alignment with a pulley 31 carried upon armature shaft 38 of a driving motor 39. The driving motor 39 is supported upon and beneath the bed plate I9. A driving belt 49 is led around the pulleys 36 and 31 to impart motion from the motor shaft 38 to the worm shaft 34. In order to drive the shaft 39 with some degree of nexibility it is desirable to use a helical spring belt.

Mounted upon the opposite end of the bed plate I9 from that occupied by the head stock i2 is the tail stock i3. This includes a standard 4! which is slidable upon the upper face of the bed plate I9 and may be set in position by a cap screw 42 which extends upwardly through a slot 43 in the bed plate. The slot 43 extends longitudinally of the bed plate so that the tail stock I3 may be disposed in a desired spaced relation to the head stock l2. The standard 4l is formed with a central horizontal bore 44 through which a cylindrical sleeve 45 may extend. The sleeve may slide longitudinally through the bore 44 and may be locked by a set screw 46 which passes through a threaded opening 41 in the upright 4l. The sleeve 45 has a central cylindrical bore 48 extending longitudinally through it to receive a tail stock spindle 49. This spindle extends outwardly from opposite ends of the sleeve. The end which projects toward the head stock l2 is formed with a central bore 59 to receive the shank 5I of a movable chuck 52. This chuck is complementary to the chuck 29 and is formed with a cylindrical wall section 53, the outer marginal edge of which has a tapered face 54. The end of the spindle 49 which receives the shank 5l of the chuck 52 is formed with an enlarged shoulder 55. Disposed between the shoulder 55 and the end face of the sleeve 45 is a spring 56 which urges the spindle forwardly, and thus yeldably holds a piece of work, indicated by dotted lines in Fig. l at 51, between the chucks 219 and 52.

The outer end of the sleeve 45 is provided with a collar 58 secured in position by a set screw 59. The collar 53 is formed with an arm 69 upon which a shifting lever 6l is mounted by a pivot pin 62. This lever swings horizontally and projects forwardly from the bed plate i9, as particularly shown in Fig. 1. A handle 83 is formed on the outer end of the lever 6i and a iinger 64 is formed on the inner end of the lever. The :linger 64 extends into a groove 65 formed in the side of the spindle 49. The shape of the end of the finger 64 and the groove 85 are such as to insure that as the lever 6I is swung on its pivot the spindle 49 will be reciprocated longitudinally within the bore 48 of the sleeve. Secured upon the outer end of the spindle is a switch arm 66 which is formed with a transverse bore 61 at its free end. Extending into this bore is a switch rod 68 which is secured adjustably by a set screw 69. The rod 68 extends horizontally and parallel to the longitudinal axis of the spindle 49 and passes above and across a gauge switch unit 19.

The gauge switch unit 19 includes a pair of switch blocks 1l and 12 between which a switch lever 13 is mounted to oscillate. As shown diagrammatically in Fig. 5 of the drawing, the block 1l carries a movable contact element 14, which engages a fixed contact 15. The block 12 carries a movable contact element 16, which engages a xed contact 11. The movable contact element 14 carries a pin 18. The movable contact element 16 carries a pin 19. These pins are disposed upon opposite sides of the switch lever 13 and may be engaged by the lever alternately to close and open electric circuits through switch blocks 1l and 12. The fixed contacts 15 and 11 are provided with conductors 89 and 9i, respectively. These are secured to a lead Wire 82 leading to one side of an input power plug 83. The opposite side of the power plug 83 is provided with a conductor 84 leading to one pole of a make and break switch 85, which is secured upon the bed plate i9. The opposite pole of the switch 85 is provided with a conductor 86 leading to one side of the driving motor 39. The opposite side of the motor 39 is provided with a conductor 81 which connects to the power lead line 82. A conductor 88 leads from one side of the switch 85 and provides a common feed wire for signal lights 89 and 99 controlled by the switch blocks 1I and 12 of the switch unit 19. A conductor 9| is connected to one side of the signal light 89, and a conductor 92 is connected to the opposite side of the signal light 89. The conduct-or 92 is electrically connected with the movable contact member 14 of the switch block 1|. A conductor 93 connects to one side of the signal light while the opposite side of the light is provided with a conductor 94 leading to the movable switch element 16 of switch block 12. Thus, when the switch in block 1l is closed the signal light 89 will be illuminated, and when the switch in block 12 is closed the signal light 99 will be illuminated. The closing of the circuits through switch blocks 1l and 12 is effected by movement of the intermediate switch lever 13, as previously described. This lever has a fork extending transversely through its free end. Within the crotch of this fork the switch rod 68 lies. Mounted upon the rod 68 at one side of the lever 13 is an adjustable collar 95 which is held in set position by a set screw 96. This collar bears against the vertical face of the switch lever 13 adjacent to the switch block 12. Upon the opposite face of the switch lever 13 a compression spring 91 is provided. This is mounted upon the switch rod 69 and is interposed between the face of the switch lever 13 and an enlarged shoulder 98 formed at the end of the switch rod 68.

The switch unit 19 and the signal lights 89 and 99 are here shown as provided forl making linear measurements. It is preferable that the two lights shall be of diierent color, as for example, the light 89 may be red and the light 99 may be yellow. The switch and its operating means are so designed as to cause the yellow light 90 to be illuminated when the piece of work 51 is too long and its measurement exceeds a plus tolerance limit of a given dimension. The red light 89 is intended to be illuminated when the piece of work 51 is too short, and the measurement is less than a minus tolerance limit of a given dimension. It will be recognized that when the measurement does not exceed the plus or minus tolerance limit neither of the lights 89 or 99 will be illuminated.

Inspection may be necessary for other linear dimensions, as for example, from the point of "and 'HIFI :aora-m I5 1oontactfo'f fthe-piece of 'work 'T51 with the 'face 332| of 'fthe :driving 'ch-nok 29 to a'shouider on the piece -of 'work. r-For l"this .purpose a @switch funit 199 is provided. Thiszunitcompriseslswitch blocks |00 These blocks are mounted on a cross Icarriage `lf02'1wihich 'restsnpon the ibed plate |.ll and is 'secured v-adg-ustaloly in 'position by a set screw |103 :passing through `a. slotted opening '11.00 in the carriage vand permitting the #carriage to ibe lmoi/fed longitud-inally'of the 'bed plate andfbe- 'tween the head-'stock |12 andthe tail-stock I3.

lviounte'd*upon the 'cross'fcarriage 1.02 @is a horlyaantal bracket |05. 'This bracket `provides a pivotal mounting for a vlertic-al oscillating post fI-06. AThe post is mounted within 'a :slot |01 vrtermed-tlirougil'i the bracket 105 and is carried on fa Apivot -pin 108. The posi; :has :a Tr-shaped -foot'proviidingiarms |2109 and `II=0 which-extend Koppos'itelyA from the f-pivot withinl the slot. 'These arms areitted with adjusting screws vI|| amd lilwhich rest-upon contact points II'3 and lI I4 of movable switchielements II |5 and rI-I=6, res-pecltively. 'The switch element I I5 *is :part of the switdhl-h'lockffl 0l). 'The switch element III6 is 'part 'of the 4switchbloc'ik Alili. i'(iomplem'entary'to the switch A#element IiIi 'is -avcontact Il'lf'I. Comple- "men'taryito therswli-tch #element Ilm 'lis a Contact `I 11B. `ktension:snr-ing IISli's mounted by one end 'upon 'the bracket N15 iandby its other end to fthe 'post *106. "This spring is intend-ed to urge the post toward a `work shoulder, and when no work is the Achuck will lclose lswitchiilock |501 it ibeingunderstood Athat `wl-ren`fascfllated around its pivot 1118 'fthe screws IlI'-'I-or Il I'2 will contact the pins I'I'3 and 21M 'of the switchfbl'ocks and close one orithe oth'erfoitiie-switches Ill0'or"I0-=I. Carriedup'on-'thefpost |015 and extending-'horizontally 'and parallel to the axis *10B-is a caliperiinger |20. "This linger `passes through-.an opening iin the .post i506 andis held in an 4adjusted position *by la se'tvsc-rew `lI'v'll Thefside of Athe caliper finger |20 is`in`t'ended `tobear against a work yace, las will be hereinafter described. The'switchzlblocks |00 and rll are connected to the feed wire 02 Tby a conductor -=`I22, which in turn is :provided fwith conductors |123 vand @|24 connecting tov the Acontact elements II L11 .and 'I I', respectively. The switch element |155 is connected by .a conductor 105410 one 'side fof .a signal light "|26, The oppofsite side :ofthe `signal flight 1,26 is-COnnected to la conductor TIQTI. 'Tiles-witch element 111.16 is .connected ite -a conductor |T28= whichleads to one vside of Aa :signal light '02.9. "The opposite side of 'the signal light iii-29 lis provided with a conductor vF31). tIt will be vseen in Fig. `5 that 'lamp -conf' (doctors '591, 03, `1I 'f2.1 and -fI30 rvare connected to the Icommon feed wire'f.

En inspection tests it is desirable to test the @parts -for ooncenftricity acoincident with the 'test 'of 'linear dimensions. In vorder to do that a prel'ci'siongauge I'3'I 'is provided and preferably has a dial |32 graduated :in thousandths and .over which an .indicatinghand |33 may swing. 'Thishand is actuated '-by mechanism within the case of the gauge Aand .connected with the center pin |134.

interposed between the .gauge mechanism and the work is a spindle |35 which rests against the work "to be measured. .'Iihe backvef .fthe Icase of the precision gauge |34 is fitted with :a lug |35 .pivoted'fby ta pin ,i130 tto la. supporting post |38. The lower @end of the .supporting Ipost is fitted `with .a ba-ll :|39 :mounted-within a socketstructure M0. The .socket .|40 is `secured :to the bed .plate :Iiaand impossible `:for -the precision gauge to lo'e property -zadusted with relation to the'work @to be inspected.

ln-vdescribing-.the operation of the present in- =vention itisirilsoia'e understood that Fig. 16 of the vdrawing merely'shows'one piece of lwork which may-be inspected infatesting device of the present type, and it'wvill'fbe irecognized'that.variations in -adjusmient made `to receive and inspect Aworlernieces of -diiierent sizes and shapes and 'havin-g diiferent critical dimensions. It is also tol-:be understood -th'atrifrequired the chucks 29 aand Elway be. interchanged with other types of holding. meansor centersin'order to accommodatef'dierentipieoes of work. The work piece 53|.,iwliiz'il11 ishere shown `inzexplaining the invenltionyiha's lbeenfselected since the critical dimensidnsfuse aftapcred face asa bench mark. This "nanticuzlar'fwork .piece is provided as a coupling ^between#the-tendsnftuloular metal conduits and 'into-which n'dsthfe 'tapered .portions III-I and fiMiZiof ttheworkiniece v51 extend. The portions tIf v*and M2 .each represent the frustum of a -con'e 'of tithe salme :dimensions It is necessary `that these-conical 'portions shall 4loe absolutely 'concentric with' threaded extensions |43 and |44 o'itheiconnlingf' so that nuts :passing over the .threaded zrportion and carrying tapered memahersffbearing against the outer face of the con- .idnit to be coupled will bear uniformly along a :piane normal :to'fthe axis of .the coupling, and -w'llaproduce {continuo-ns .line contact `between the mrtwardzlyS-armg 'rend of the conduit and the 'ifmstoconzical end of fthe coupling. Thus, two "criticaiclimensions `are .an overall dimension from fthe ariane-of line contact of the faces 3| and -54 .of-the' ch11cks 1l-Sand "52, rand dimensions representing-fthe concentricity-o'f the threaded portional-13'fand 'fi with relation to the portion lof iiheommical-endslfll and M2. The first of these lfori'ficxad *dimensions is indicated as A in Fig. 6 rinfime'drawing, zand :th'esecond of these dimen- Ysions;isfindicated as B. Another critical dimenrsion'imatheicnupling 51 is the distance from the fplanesoficontactioi the chucks with the cones I4I :and MZ-itoeshoulders 14S-and M6 of a hexagonal Iportionfilf'lfzat the center 'of the coupling. These =fdimensions 4are :indicated as Cin Fig. 6. It will lee Iassisuned#that :a :certain :amount of tolerance :islpermissible the critical dimensions are Arplus terminus .002,.B plus or minus .005, and plus lor :minus .002. The instrument is `then @repaired .tor v:use by selecting and installing the .proper ichucks T20 and @52, Aor other centering .mem1s,:ater which the tail stock I3 is adjusted ll'long-itudinalily .to bedplate I0 to accommodate .thewonk piece 5L .The tail stock is then clamped .in position bythe set :screw l42. The sleeve 4'5 within .the itail stock may be adjusted also by .untighteninfg Ascrew `46. This will permit the .fsleeve-#Ifand lt-he spindle 4'9 to move as a unit, v:and iwillgeitain uniform tension upon the spring 56. r.Hefter this adjustment has been made the screw @16 may'he tightened. The switch unit I0 is thenadiustedfor dimension A and by looseningfthefset'sorewrS `to move the switch rod 58 appropriately, 4.and Sthen loosening the set screw 916 y:to 'move the adjusting lsleeve 05, the lamount -of'ltdlerance in .-dimensionfA vmay vbe determined accurately. these .adjustments have been rricade the seti screws-@Sand SG'may be tightened -encthef'switchzrod :68. The carriage v|02 `may then be adinet-editan"thebedrplate I0 by releasing the :set screw-zilfeand .sliding the carriage along until {theside atane'of the caliper .finger |20 assumes 'ia desiredgmsiton with relation Ito `the plane 'of contact of the faces 3| of the chuck 29. When the side face of the caliper nger l2@ is in a properly set position the post Hit, which carries it, will be standing substantially vertically, and the set screws and H2 will be adjusted to have an equal space between them and the pins |I3 and ||l| of the switch blocks it@ and |95. The set screws ill and |52 will also be adjusted so that the normal space between them and the pins will represent the amount of tolerance in the dimension C. The precision gauge i3| is then adjusted so that when the end of its spindle rests against the circumference of the work, such for example as the circumference of the threaded ends M3 and |44 the index hand |33 will stand at zero on the dial H32. This will represent the precise diameter of the work piece being inspected, and as the diameter varies in concentricity the indicating hand will swing toward plus or minus graduations. The machine thus adjusted is ready for use in inspecting parts, it being understood that the plug 83 has been connected with a suitable source of electric supply to provide energy for the motor (S9 as well as current for the gauge lights SQ, 9d, i2i and i229. The work may then be placed in the device, as indicated in Figs. l and 6. I-l'ere it will be seen that the chuck faces 3| and 54 will contact the faces of the frustoconical members itl and M2 at a point midway the length of these members. The work is placed between the chucks 29 and 52 by swinging the lever ti in the direction oi the arrow a in Fig. l. This retracts the spindle it against the action of the spring 5t. As this movement takes place the spring Si' on the switch rod 63 will also be compressed. When the lever 6| is released the parts will be restored to their original positions and the machined part 5'! will be clamped between the chucks 29 and 52. The switch 85 may then be closed to deliver a supply of current to the wiring system. This will cause the motor to be energized so that the driving spindle I8 will be rotated through the driving belt itil, the worm 33, and the worm gear 32. When the work is thus placed the side face of the caliper finger will bear against the face M5 of the work piece 51, and the precision gauge 53| may be swungI over the work until the end of its spindle 35 contacts the circumferential face of the threaded portion i435. When the lever iii is released the lmovable switch element 'lt of the switch unit 'i0 will be disposed in a relation to the Contact pins 'iS and 'i9 of the switch blocks 'il and 'i2 as determined by the dimension A on the work piece. In the event that the distance A, as represented by the transverse planes contacted Iby the chuck faces 3| and 54, is greater than the absolute dimension the switch lever i3 will be drawn toward the block it, and if the variation is suciently great to establish an electric circuit through the switch block l2 to the gauge light ai?, this will then be illuminated, and will indicate that the dimension A exceeds the limited amount of tolerance. The work piece 5l may then be immediately removed from the instrument and returned for reworking. If, however, the distance A is less than the minus amount of tolerance the switch lever 13 will swing toward the switch block 'il and establish an electric circuit through the gauge light 859. This will indicate that the dimension A is too short and will necessitate in placing this particular' part into scrap. A test is concurrently made for the dimension C on the threaded end |43 of the work piece. If the distance from the plane of contact of the face 3| of the` chuck toV 'the shoulder VMI5 on the work piece is greater than desired the post |06 will swing to establish an electric contact through the switch block IUI, which. will energize the gauge light |29 and indicate that this distance is too long. If the distance C is too short the circuit in the switch block itl will be closed, thus completing the circuit through the gauge light |26. During this time the indicating hand on the precision gauge I3| may fluctuate at opposite sides of the zero graduation, and if this fluctuates more than the required plus or minus tolerance the inspection report will indicate that there is an undesired amount of eccentricity of the threaded portions with relation to the axis of the work piece. It will of course be recognized that in the event none of the gauge lights are illuminated the critical dimensions A and C of the work piece are within the plus or minus tolerance limits. It also should be pointed out that after the dimension C of the portion |553 of the work piece has been measured it is necessary to remove the work piece from between the chucks and reverse it so that the length of the portion |44 may be measured.

It will thus be seen that by the use of the testing instrument here described it is possible to measure linear overall lengths and intermediate overall lengths of parts quickly and with micrometer precision even though the parts are difcult to measure by ordinary methods, and furthermore, that it is possible to inspect a Part for variation in concentricity with great accuracy, the instrument being simple in construction, not liable to get out of order, and being so designed as to make it possible for relatively unskilled workmen to operate it satisfactorily.

While I have shown the preferred form of my invention as now known to me, it will be understood that various changes maybe made in combination, construction and arrangement of parts by those skilled in the art, without departing from the spirit of my invention as claimed.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

l. A testing device to receive a work piece to be inspected and upon which linear dimensions are to be measured, which comprises a base structure, a fixed bearing standard carried thereby, a movable bearing standard carried thereby, means whereby the movable standard may be set adjustably with relation to the nxed standard, a spindle mounted upon the fixed standard and held against longitudinal movement, a spindle mounted upon the movable standard and adapted to be longitudinally movable, a pair of chucks, one carried by the fixed spindle and one carried by the movable spindle and between which the article to be tested is held, switch actuating means associated with the movable spindle, a two-way switch operated by said switch actuating means, one of said switch elements being closed in the event the length of the portion of the article to be tested and occurring between the chucks is greater than a predetermined distance and the other acting when the article to be tested is less than a predetermined distance, and means associated separately with said switches to indicate the operation of the same.

2. The structure of claim 1 including adjusting means interposed between said switch actuating means and the two-way switch whereby the degree of tolerance may be established.

3. A testing device to receive a work piece to be inspected and upon which linear dimensions are to be measured, which comprises a base structure, a fixed bearing standard carried thereby, a movable bearing standard carried thereby, means whereby the movable standard may be set adjustably with relation to the fixed standard, a spindle mounted upon the Xed standard and held against longitudinal movement, a spindle mounted upon the movable standard and adapted to be longitudinally movable, a pair of chucks, one carried by the xed spindle and one carried by the movable spindle and between which the article to be tested is held, said chucks being designed to establish line contact with the article being tested and between which lines of contact a measurement is taken, switch actuating means associated with the movable spindle, a two-way switch operated by said switch actuating means, one of said switch elements being closed in the event the length of the portion of the article to be tested and occurring between the chucks is greater than a predetermined distance and the other acting when the article to be tested is less than a predetermined distance, and means associated separately with said switches to indicate the operation of the same.

JOHN B. LOVICK.

REFERENCES CITED The following references are of yrecord in the le of this patent:

UNITED STATES PATENTS Number Name Date 454,516 Brown June 23, 1891 652,622 Marshall June 26, 1900 952,588 Stevens Mar. 22, 1910 1,317,459 Rouanet Sept. 30, 1919 1,319,361 Rouanet Oct. 21, 1919 1,389,341 Blood Aug. 30, 1921 1,667,109 Garlent Apr. 24, 1'928 1,832,511 Settem Nov. 17, 1931 1,900,231 Ede Mar. 7, 1933 2,030,237 Brittain Feb. 11, 1936 2,047,408 Emery et al July 14. 1936 FOREIGN PATENTS Number Country Date 325,063 Germany Sept. 8, 1920 

